Power-quality events and operation transients in power systems (PS) with isolated neutral
can saturate inductive voltage transformers (IVT), which, when interacting with the overhead and
underground cable capacitances, can cause ferroresonance events in the local PS. This abnormal
operating mode can partially or totally damage the transformers and switchgears within the affected
PS. Distribution system operators (DSO) can minimize these effects by detecting ferroresonance events
accurately and fast enough and changing the mode of operation accordingly. Direct detection methods,
i.e., based on voltage measurements, are reliable, but the massive deployment of this solution is
relatively expensive; i.e., power quality analyzers cost thousands of USD. Alternatively, indirect
detection methods are also available, e.g., IVT vibration measurements with accelerometers costing
hundreds of USD, but their reliability depends on the installation method used. This manuscript
proposes using the acoustic noise caused by magnetostriction forces within the IVT core during
ferroresonance events to detect their occurrence. Compared to other indirect methods, electret
condenser microphones with preamplifying stage cost less than USD 10 and are less sensitive to
the installation procedure. The proposed method is validated experimentally, and its performance
compared to IVT vibration measurements one by using the same detection methodology.
